Production of sulfur trioxide addition products



PRODUCTION OF SULFUR TRIOXIDE ADDITION PRODUCTS Everett E. Gilbert, Morristown, and Henry R. Nychka, Shongnm Lake, NJ., assignors to Allied Chemical Corporation, New York, N'.Y., a corporation of New York No Drawing. Application October 29, 1958 Serial No. 770,272

11 Claims, .(Cl- 260-2948) The present invention relates to addition products of organictertiary nitrogen bases and sulfur trioxide. More particularly, the invention relates to improved processes for the production of high yields of addition products of organic tertiary nitrogen bases and sulfur trioxide.

- .There are several methods known for the preparation of addition products of organic tertiary nitrogen bases and sulfur trioxide. For example, U.S.P. 2,739,150 of March 20, 1956, describes the preparation of these addition products by reacting the organic base with sulfur trioxide' in the absence of solvent. Also, the addition productshave been made by carrying out the reaction in the presence of organic solvents, such as chloroform and carbon tetrachloride. Both of these procedures (i.e., with or without organic solvent) are inefficient and generally unsatisfactory. When no solvent is used, decomposition occurs with lowering in quality of the addition products. When an organic solvent is used, the quality of the addition products is also low.

' An object of the present invention is to provide improved processes for producing high yields of addition products of organic tertiary nitrogen bases and sulfur trioxide.

A further object of the invention is to provide efficient and economical processes for producing high yields of addition products of organic tertiary nitrogen bases and sulfur trioxide having improved quality.

Other objects and advantages of the invention will be apparent from the following description and examples. .A ;cording to the present invention, the above objects are realized by reacting an organic tertiary nitrogen base withsulfurdioxide .to form'a sulfur dioxide complex, and then reacting the sulfur dioxide complex with sulfur trioxide, said organic base and sulfur trioxide being employed in stoichiometric quantities. -jfflfheforganic"tertiarynitrogen' bases employed in the process of'th'ei present invention may be pyridine, dir'iiethylafniiine," t'rirriethyla'mine, triethylamine, tripropyla'fimie, tributylamine, dimethylbenzylamine, cyclohexyldimethylamine, N-methyl 'morpholine, the picolines and other similar prganic tertiary nitrogen bases. As desired or required, the base may-be introduced in either gaseous orliquid form.-- 1he sulfur:trioxideemployed may be derived from any suitable source and maybe .in either gaseous or liquid form. However, we have found that the sulfur trioxide is conveniently used in stabilized liquid form.

g ts preferred, a mono-sulfur trioxide addition product is produced by employing the prganic tertiary nitrogen baseand: sulfur ,trioxide in equimolecular quantities. We have found that if anexcess of either, ofthese reactants isused, theiquality ofthe mono-sulfur trioxide addition product is lowered. However, it. is within the scope of present invention "to employ the reactants in ratio of two mols ofsulfur-trioxi'de to one mol of organic base in order to produce-a ii-sulfur trioxide addition product.

2,928,835 Patented Mar. 15, 1960 (1) C H N+SO C H N.SO

sulfur dioxide complex mono-sulfur trioxide addition product or (3) C H N.SO +2SO C H N.2SO +SO di-sulfur trioxide addition product A preferred embodiment of the present invention involves forming the sulfur dioxide complex by reacting the organic tertiary nitrogen base with at least about a stoichiometric amount of liquid sulfur dioxide. In this process, the sulfur dioxide acts not only as reactant but also as reaction solvent.

The process of the preferred embodiment is generally carried out by introducing liquid sulfur dioxide into a reactor which permits efficient cooling and agitation of the reactants. The organic tertiary nitrogen base is then added to the liquid sulfur dioxide, preferably below the surface thereof, the sulfur dioxide being refluxed at its boiling point, i.e., at about 10 C. Finally, sulfur trioxide is added to the reaction mixture to convert the intermediate surfur dioxide complex into the corresponding sulfur trioxide addition product.

The sulfur trioxide addition product is obtained in slurry form. Sulfur dioxide is evaporated off from the slurry by heating and may then be recycled in liquid form as charge to the reactor. Stirring action should be employed during sulfur dioxide evaporation in order to prevent lump formation and facilitate product removal from the reactor. For example, a pug mixer or ball-type mixer may be suitably used. The dry cake, if desired, may be 'slurried with cold water, filtered and washed with additional water to produce a sulfur trioxide addition product which is for all intents and purposes substantially pure.

We have discovered that when addition products of organic tertiary nitrogen bases and sulfur trioxide are formed by reacting the organic base with sulfur trioxide dissolved in solvents, including liquid sulfur dioxide, the resultant addition product usually contains substantial amounts of by-product acids which may render the prod-- uct unsuitable for certain industrial uses. If these acidic materials are present in too large quantities, the addition product may even become gummy instead of free-flowing. On the other hand, by carrying out the process in accordance with the present invention, the addition products are produced not only in high yield but also with reduced formation of acidic by-products;

In order to determine the amount of acidic materials (acid equivalent value) present, the addition product is slurried in distilled water maintained desirably at a temperature of about 20 to 40 C. The aqueous solution is filtered from the addition product and is then titrated with 0.1 N.NaOH solution to a permanent pink color of phenolphthalein indicator. Theoretically, pure addition product possesses no acid equivalent value. This value is therefore 'a measure of purity; the lower the value the purer the product. The acid equivalent value, e.g., of a mono-sulfur trioxide addition product, may be expressed in terms of mols of caustic soda consumed per'mol of addition product. Assuming that the acidic impurities are monobasic having molecular weights equal to-that of theaddition product, the quality of the addition product may he expressed in terms of percent assay as follows:

percent assay=(1-acid equivalent) X100 The intermediate sulfur dioxide complex may be produced in almost quantitative yield by employing the liquid sulfur dioxide in at least stoichiometric quantity with respect to the organic tertiary nitrogen base. Moreover, in order to produce a reaction mixture of sulfur trioxide addition pro-duct and sulfur'dioxide which is sulficiently fluid for pumping and heat removal, it may be necessary to employ a stoichiometric excess of liquid sulfur dioxide. Excellent results have been obtained when such an excess of liquid sulfur dioxide is used that the weight radio of liquid sulfur dioxide to sulfur trioxide addition product is maintained in the range. of about 1.5 to 4,3;1, and preferably about 3 to 4:1. i

The reactions of this embodiment of the invention are conveniently carried out at the boiling point of liquid sulfur dioxide, i.e., at about C. However, it is equally suitable to operateunder 'supei'atmospheric pressure at a higher temperature, say up to about 100 C. For example, if a temperature of about 50 to 60 C. is used, the corresponding pressure will be about 100 to 150 p.s.i.g. At these temperatures water may be suitably used as coolant. When operating at atmospheric pressure, as preferred, refrigeration is required for condensing the refluxing sulfur dioxide during the reaction.

In using superatmospheric pressure, a pressure-resistant reactor equipped with a jacket or coils for water cooling is charged with liquid sulfur dioxide at about room temperature. With cooling and agitation the organic base is added as rapidly as possible, maintaining the internal temperature, e.g., at about 50 to 60 C. Then addition of sulfur trioxide is begun, also with cooling and agitation. After addition of the sulfur trioxide, the sulfur dioxide is vented with continued agitation and warming to maintain the temperature at about 50 to 60 C.

Although the process of this embodiment of the invention may be conveniently carried out by reacting the organic tertiary nitrogen base with liquid sulfur dioxide, followed by addition of the sulfur trioxide to the intermediate sulfur dioxide complex, any other mode ofreactant addition which results in formation of the sulfur dioxide complex before appreciable reaction with sulfur trioxide may be followed with realization of the objects of the invention. For example, a solution of the organic base, in liquid sulfur dioxide may be added to liquid sulfur trioxide, preferably dissolvedin a solvent such as liquid sulfur dioxide.

Inaddition to obtainment of high yields of sulfur trioxide addition product having improved quality, the use of liquid sulfur dioxide as set forth above possesses severalv other advantages. It has a favorable boiling point (about-10 C.) for functioning as an auto-refrigerant and for easy and complete recovery. Moreover, less liquid sulfur dioxide is required than when using organic solvents. This means that smaller and less expensive equipment may be employed.

According to another embodiment of the-present invention, the sulfur dioxide complex may be formed by reacting the organic tertiary nitrogen basewith sufur dioxide in the presence of aninert organic. solvent. Although the sulfur dioxide may be employed in liquid form, itis used preferably as a gas. Efficient operation is realized by employing the. sulfur dioxide in about stoichiometric amount with respectto the organic base. Although larger amounts of sulfurdioxidearenot detrimental, they are unnecessary .anduneconomical.

Suitable, inert organicfsolvents include; halogenated (preferably chlorinated) hydrocarbons. such as ethylene chloride, methylene chloride, chloroform, tetrachloroethylene, dichlorodifluoroethylene, etc. The.solvent islkr s i W ht tio F a im, ga da add i n PXQ not of at least about 2:1, and preferably about 2101051 In this embodiment of the invention, operation above about 10 C. is permitted without using a pressure vessel. Thus, suitable reaction temperature ranges from about 0 to 50 C. Moreover, when gaseous sulfur d-ioxide is used, the added expense of liquefying sulfur dioxide is avoided.

The addition products of organic-tertiary nitrogen bases and sulfur trioxide prepared in accordance with the processes of the present invention are, extremely useful to:- agents for sulfonation, sulfation and snlfarnation, "e,g., in the production of leuco vat; dyes, sulfated. carbohydrates, sulfamates, etc.

The invention may be illustrated by the following examples in which parts are by weight;

Example I 538 parts of liquid sulfur dioxide were placed in a glass reactor equipped with a Dry leecond'eusen and a mechanical stirrer-and cooledin a Dry, Ioe-acetouebajth so that the sulfur dioxide. refluxed atitsboiling. oint (about l0 C.). 1 58.2 partsof liquid pyridine were. added to the refluxing sulfur; dioxide with stirring over a 20-minute period. Then 160, parts of; Sulfan (stahilized liquid sulfur trioxide) were added with stirring over a 60-minute period. Sulfur-dioxidewas evaporated; oh, and remaining traces of sulfurdipxidegwereremoyedg by drying in a vacuum desiccator. The residue; comprised the monosnlfur trioxide addition product of pyri: dine. 308 parts of the addition product; representing-a yield of 97% of theory were obtainem. Analysis oftheproduct gavean acid equivalent value-of 0,04; 96% assay).

' Example 2:

313 parts of liquid sulfur dioxide were placed in the apparatus of Example I. 39.5 parts" of liquid pyridine were added to the refluxing: sulfurdioxide with stirring over a 20-minute period; Then 40 parts of Sulfan" were added-with stirring overa BO-minute-period. Sulfurdioxide was exaporated off, and remaining-traces of sulfur dioxide were removed by drying in a vacuum desiccator. The residue comprised the mono-sulfur trioxide addition product of pyridine. 78 parts ofthe addition product, representing a yield of 98% ofthcory, were obtained. Analysis of theproductgaveanacid equivalent value of. 0.07 (93% assay).

When a pyridine-sulfurtrioxide. addition product-was prepared under similar conditions except forreacting pyridine with sulfur trioxide dissolved: inliquid sulfur dioxide, the addition product had anassayi of'only (acid equivalent -value= 0 .1 5-)-.

Example" 3* The u ids dditicapmduct f-lny dinesia's" prepared asfollows. 433 partsioflliqu fl H QIfdlQ IdQ. were placed in the apparatus ofiExample 1. 39.5 paftx ofliquid pyridine wereadded to the refluxing sulfur dioxide with stirring. Then 80' parts of"Sulfan"- were added with stirring. The total time of addition-was 45" minutes. Sulfur dioxide was evaporated-olfg andresidual sulfur dioxide was removedby dryingina vacuum desiccator. The residue was the di-sulfur-trioxide'addl' tion product of pyridine. 114gpartsofthe addilionprod uct, representing a yield: Of-F95-495 of: theory; wow obtained.

522 parts of liquid sulfurdioxidewete placed in the apparatus of Example 1. 56--parts ofliquid trimethylamine} were added to the refiuxingsulfur dioxide with" stirring over a 15 -minute period. 38--partsof -Sulfan" were added; to one-half of the 'sulfurdioxide-acomplexvso-formedwith stirring oven a period of-FZGminuts. Sulfur dioxidflmj' evaporatedv off, andrresidual sulfur-dloxidewwas=- removed by. drying in a vacuu-rnldesiccator The m-aquarium: pr d. 6 par -sci. t e monmsuli. maids-amounted:

- net of trimethylamine. This amount of addition product constituted 98% of theory. Analysis of the addition product gave an acid equivalent value of 0.19 (81% assay).

25-minute period, followed by additional stirring for 30 minutes. The temperature was then raised to 40C. to drive out the sulfur dioxide into the Dry Ice trap. The resultant slurry was filtered, washed with about 243.7

Example 5 Parts of fresh tetrachloroethylene and dried to constant weight. The residue, a nearly whitepowder, comprised ggs gg g gl g hi gi gg x i gg fg g gi the mono-sulfur trioxide addition product of pyridine. amine were added to the refluxing Sulfur dioxide with 79.8 parts of the addition product, representing a yield stirring over a 40minte perioi Then 177 parts of of 99% of theory, were obtained. Analysis of the product Sulfan were added to about one-half of the sulfur digave an acld equivalent value? 7 assay) oxide complex so formed with stirring over a period of when a pyndlileisulfur lde addmon product was 1 houm Sulfur dioxide was evaporated 0E, and prepared under similar conditions, except that no sulfur residual sulfur dioxide was removed by drying in avaouum dloxldF used the adfhtlolt P ct Was a tan, pasty desiccator. The residue comprised 298 parts of the mono- F matenal whlch had an acld equivalent value of (27% sulfur trioxide addition product of trimethylamine. This assay): amount of addition product constituted 97% of theory. i We have descnbed certain for Analysis f the product gave an acid equivalent value carrying out the processes of our invention, t will be f 1 assay) apparent that many changes may be made without de- When an addition product of trimethylamine and sul- Partmg from the P of the fur trioxide was obtained under similar conditions except 20 We claim: for reacting trimethylamine with sulfur trioxide dissolved A Process of Preparing all addition Product of an in liquid sulfur dioxide, the addition product had an assay Orgahih tertiary nitrogen base and sulfur trioxide which of only 57% (acid equivalent va1ue=0,43), comprises reacting an organic tertiary nitrogen base se- Example 6 lected from the group consisting of pyridine, dimethylaniline, trimethylamine, triethylamine, tripropylamine, 389 Parts Of liquid Sulfur dioxide were P in the tributylamine, dimethylbenzylamine, cyclohexyldimethylapharatus of Example A gaseous stream of hy amine, N-methyl morpholine and picolines with at least 11111111? was Passed through a towel of s'mesh calcltlm about a stoichiometric amount of sulfur dioxide, thereby Chlorlde- The g was cfmdehseda h pafts f 'f forming a sulfur dioxide complex, and reacting the sulfur were added t the fethlxlllg Sulfur dloxlde wlth stlll'lhg dioxide complex with sulfur trioxide, said organic base Over a 15-mlhl1te p f Then 68 Parts of sulfatf' and sulfur trioxide being employed in stoichiometric were added with stirring over a 30-minute period. i i Sulfur dioxide solvent was evaporated off, and residtlal 2. A process of preparing a mono-sulfur trioxide addi- Sulfm' dloxlde f removed by drymg 9 tion product of an organic tertiary nitrogen base which cater The re.sldue was.the mono'sulfur moxlde i i 0 comprises reacting an organic tertiary nitrogen base seproduct of trimethylamine. l17 .5 parts of the addition lected fmmthe group consisting of pyridine dimethy} f p g g f i f of g q o aniline, trimethylamine, triethylamine, tripropylamine, of fg gi g a gave an ac en tributylamine, dimethylbenzylarnine, cyclohexyldimethyl- This example shows slight improvement in quality amine i i mqrpholme and Plcolme? l at least of addition product when the trimethylamine reactant was aboul a i amount of sulfur dlqxlde thereby dried with calcium chloride before use. forming a sulfur dioxide complex, and reacting the sulfur dioxide complex with sulfur trioxide, said organic base Example 7 and sulfur trioxide being employed in equimolecular quan- 286 parts of liquid sulfur dioxide were placed in the 5 titiesapparatus of Example 1. 50.5 parts of liquid dimethyl- A process of p p a mono-sulfur io e ddianiline were added to the refluxing sulfur dioxide with tion Pf Of an Organic tertiary nitrogen base which stirring over a 15-minute period, followed by 40 parts comprises reacting an organic tertiary nitrogen base seof Sultan over a 30-minute period. Sulfur dioxide was lected from the group consisting of Pyridine, dimethylevaporated 0E, and residual sulfur trioxide was removed 59 aniline, trlmethylamine, tfiethylamine, tripropylami by drying in a vacuum desiccator. The residue comtyl m dimethvlbenzylamine, cvclohexvldimethvlprised the mono-sulfur trioxide addition product of diamine, y morpholine and Picolihes with a stoimethylaniline. 100 parts of the addition product, repchiometric excess of liquid sulfur dioxide, thereby formresenting a yield of 100% of theory, were obtained. ing a sulfur dioxide complex, and reacting the sulfur Examples 1 to7 are summarized in the following table: dioxide complex with sulfur trioxide, said organic base Example Example Example Example Example Example Example 1 2 a 4 5 6 7 organic base pyridine pyridine pyridine trime thyltrimethyltrimethyl dimethyl amine amine amine aniline 2.0 0.5 0.5 0. 47 2.22 0.85 0.5 2.0 0.5 1.0 0. 47 2.22 0.85 0.5 -10 -10 -10 l0 10 -10 10 1.8 3.0 3.8 3.9 1.5 3.3 2.9 97 9s 9s 97 100 100 assay 97 s3 s1 s0 s7 Example 8 and sulfur trioxide being employed in equimolecular 500 parts of tetrachloroethylene and 39.5 parts of quammes' pyridine were mixed in a reactor equipped with a Dry 4. A process of preparing a mono-sulfur trioxide addilce trap, a mechanical stirrer and an external bath. 70 orgamc F Y mtrqgen base Whlch 35 parts of dry sulfur dioxide gas were introduced into compnses reacting an rga11c temary f f 1 the vessel over a 30-minute period with stirring and cool- Q firon} the group cons sting of pyridine, dunethyling to a temperature of 22 to 30 0. The reaction amlme. trlmethylamme, trlethylamme, u ps mixture was further cooled to 0 to -s 0., and 41 parts t i v i dimethylbenzylamine. cvclohexyldimethylof Sultan were added dropwise with stirring over a 15 amino, N-methyl morpholine and picolines with at least about a; stoichiometric amount of sulfur dioxide in the" presence of an inert organic solvent, therebyforming a sulfur dioxide complex, and reacting the sulfur dioxide complex with sulfur trioxide, said organic base and sulfur trioxide being employed in equimolecular quantities.

5. A process of preparing a mono-sulfur trioxide adclition product of pyridine which comprises reacting thepyridine with a stoichiometric excess of liquid sulfur dioxide, thereby forming a sulfur dioxide complex, and-reacting the sulfur dioxide complex with sulfur trioxide, said pyridine and sulfur trioxidebeing employed.v in equimolecular quantities. 1

6. A process of preparing a mono-sulfur trioxide addiv tion product of pyridine which comprisesv reacting the pyridine with at least about a stoichiometric amountof.

sulfur. dioxidein the presence of an inert organic solvent, thereby forming a sulfur dioxide. complex, and. reacting the sulfur dioxide complex. with sulfur trioxide', s a'id.

the dimethylaniline with at least about a stoichiometric' amount of sulfur dioxide in the presence of an inert organic solvent, thereby forming a sulfur dioxide complex, and reacting the sulfur dioxide complex with sulfur trioxide, said dimethylaniline and sulfur trioxide being employed in equirnolecular quantities.

9. A process of preparing a mono-sulfur trioxide'addh tion product of trimethylamine which comprises reacting the trimethylamine with a stoichiometric excess of liquid sulfur dioxide, thereby forminga sulfur dioxide complex,- and reacting, the sulfur dioxide complex with sulfur trioxide, said trimethylamine and sulfur trioxide being emlayed in equimolecular quantities.

10. A process of preparing a mono-sulfur trioxide addition product of trimethylamine which comprises reacting the trimethylamine with at least about a stoichiometric amount of sulfur dioxide in the presence of an inert organic solvent, thereby forming a sulfur dioxide complex, and reacting the sulfur dioxide complex with sulfur trioxide, said trimethylamine and sulfur trioxide being employed in equimolecular quantities.

11. A process'of' preparing a mono-sulfur trioxide addition productof an organic tertiary nitrogen base which comprises reacting arr organic tertiary nitrogen base selected from the] group consisting of pyridine, dimethylaniline, trimethylamine, triethyl'amine, tripropylamine', tributylamine; dimethylbenzylarnine, cyclohexyldimethylamine, N-methyl morpholine and picolines with a stoichiometric' excess of? liquid sulfur dioxide, thereby forming a sulfur dioxide complex, and reacting the sulfur dioxide" complex with sulfur trioxide, said organic base and sulfur trioxide being employed in equimolecular quantities and the weight ratio of liquid sulfur dioxide to sulfur trioxide addition product being in the range of about 1.5 to 4.3:1.

ReferencesCited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Mme et aL: J. Am. Chem. Soc., vol. 11, pp 852-8 1949 

1. A PROCESS OF PREPARING AN ADDITION PRODUCT OF AN ORGANIC TERTIARY NITROGEN BASE AND SULFUR TRIOXIDE WHICH COMPRISES REACTING AN ORGANIC TERTIARY NITROGEN BASE SELECTED FROM THE GROUP CONSISTING OF PYRIDINE, DIMETHYLANILINE, TRIMETHYLAMINE, TRIETHYLAMINE, TRIPROPYLAMINE, TRIBUTYLAMINE, DIMETHYLBENZYLAMINE, CYCLOHEXYLDIMETHYLAMINE, N-METHYL MORPHOLINE AND PICOLINES WITH AT LEAST ABOUT A STOICHIOMETRIC AMOUNT OF SULFUR DIOXIDE, THEREBY FORMING A SULFUR DIOXIDE COMPLEX, AND REACTING THE SULFUR DIOXIDE COMPLEX WITH SULFUR TRIOXIDE, SAID ORGANIC BASE AND SULFUR TRIOXIDE BEING EMPLOYED IN STOICHIOMETRIC QUANTITIES. 